Recently I ran into a strange issue where the Intel NIC was showing dropped packets on the interface. This particular server was having other issues (performance-ish type) so we were eager to get to the bottom of this.
Symptoms and interesting finds…
- ifconfig shows dropped packets only for RX
- The sum of rx_flow_control_xon+rx_flow_control_xoff from ethtool -S exatly matched #1 above. The count was reset at some point and we didn’t figure this out until later. Rebooting the server helped getting our minds clear and reset this.
- While tcpdump is running the dropped packet count would never increase.
- tcpdump wouldn’t show whatever was being dropped. I guess this is why they are dropped, no?
A solution, though not perfect was finally discovered. Disable BPDU/STP on the switch. The environment only had one switch so it wasn’t huge issue. On the Cisco the command was:
no spanning-tree vlan 1,100,168,216
Some interesting resources on this:
- Title : #477 igb driver, flow control packets being dropped?https://sourceforge.net/p/e1000/bugs/477/
- Title : Mystery RX packet drops on SLES11 SP2 every 30 sec